Communication antennas on Earth-orbiting satellites typically include a reflector to shape and focus the radio frequency (RF) beam to provide the desired ground coverage. To survive the launch loads and maintain surface accuracy, conventional systems provide backside stiffening structures of composite laminate and/or sandwich panel construction. As the frequency of the RF system increases, the required accuracy of the reflecting surface increases.
Traditional backside stiffening structures for space-based antenna reflectors are constructed of reinforced composite membrane or honeycomb sandwich construction using high-strength fibers such as graphite with a resin such as epoxy. The reflecting shell is typically attached to the backside structure by bonding using discrete or continuous bonds with or without localized shear clip or edge-bond enhancing features along the stiffening structure at the intersection of the structure and the backside reflecting shell. The backside stiffening structure is unique to the reflecting surface in that it is cut to fit the contour of the reflecting shell. Each unique RF surface profile results in a unique design solution for the backside stiffening structure. Creating a new backside structure for each reflecting surface profile increases the recurring cost of the reflector design and fabrication and drives recurring schedule.
In addition, low mass and low cost antenna reflectors used on satellites may show surface distortion over time. The surface distortion can be due to manufacturing process variations or environmental stress resulting from thermal or hygroscopic effects. The surface distortion in antenna reflectors can cause a loss in the efficiency of the antenna that has to be compensated by the rest of the chain, adding cost and increased power requirements. The compensation to be performed by the rest of the chain can be expensive, if not impossible.
The surface distortion problem is conventionally solved by making backing structure ribs and rings very stiff and weighing the reflector shell down on its mold during attachment. This solution may add structural mass to the resulting antenna and may not guarantee to work, since the built-in stress may cause errors that are hard to predict beforehand.